Doc: Create and apply attributes for ECS default messaging

[karenzone]

We need a way to consistently message ECS default status across plugins. By carefully crafting and applying a shared attribute, we can ensure that the messaging is consistent across plugins. This approach also ensures that the text doesn't diverge over time from plugin to plugin.

If we need to change or tweak the info, we can update text in the attribute (and corresponding attribute in the VPR attributes file), and have the updates reflected in all plugins where the attribute is used.

Set up framework

• Create shared attribute files for use in plugin docs. Set up :include: statements to make attributes available.
  • LSR: Doc: Add shared attribute for messaging ecs default info #13083
  • VPR: VPR: Add attribute for ecs default logstash-docs#1128
• Refine messaging for ecs_compatibility defaults
  • LSR: Doc: Update attribute for ECS messaging wrt default (LSR)  #13427 Doc: Fix link in attribute #13462
  • VPR: Doc: Update attribute for ECS messaging wrt default (VPR)  logstash-docs#1217
• Test. Test. Test.
  • LSR: TEST ONLY - DO NOT MERGE: Validate ECS attr for LSR logstash-docs#1218
  • VPR: TEST ONLY - DO NOT MERGE: Validate ECS attr for VPR logstash-docs#1222
• Backports
  • LSR to 8.0:
  • VPR: N/A (The VPR is not stack versioned, so backports don't apply.)
    IMPORTANT: Set up and validate the attributes for both the Logstash Reference and the Versioned Plugin Reference before applying the attributes. Otherwise, we'll crash the doc build.

Next steps

• Apply attribute to plugin doc source files.
  • Replace current hard-coded text in plugin with attribute
  • Test locally
  • Bump versions, and publish
• Plan: Start by testing one plugin, publishing it, and validating it for both the LSR and VPR docgen process.